Java
Types and collections, OOP, generics, concurrency, the JVM and memory management.
What Java is for and how it differs from other languages, the JDK and JRE, compilation to bytecode and running a program on the JVM.
Questions coming soon
Primitive and reference types, autoboxing, type conversion, operators, branching and loops.
Questions coming soon
Declaring and overloading methods, pass-by-value semantics, varargs and variable scope.
Questions coming soon
Arrays, the Collections Framework hierarchy — List, Set, Map, Queue — and choosing the right structure for a given task.
Questions coming soon
String immutability, the string pool, StringBuilder versus StringBuffer, output formatting and regular expressions.
Questions coming soon
Classes and objects, encapsulation, inheritance, polymorphism and abstraction as Java actually implements them.
Questions coming soon
Access modifiers, static and final, constructors and initializer blocks, nested and anonymous classes, and how interfaces differ from abstract classes.
Questions coming soon
The Throwable hierarchy, checked versus unchecked exceptions, try-catch-finally, try-with-resources and custom exception classes.
Questions coming soon
Generic classes and methods, type bounds, wildcards and type erasure at compile time.
Questions coming soon
Lambda expressions, functional interfaces, method references, the Stream API and Optional.
Questions coming soon
The JVM memory model, stack and heap, garbage collection, class loading and what causes memory leaks.
Questions coming soon
Threads and their lifecycle, synchronization and locks, java.util.concurrent, thread pools, deadlocks and race conditions.
Questions coming soon
Byte and character streams, readers and writers, serialization, the NIO package with channels and buffers, and the file system API.
Questions coming soon
Reflection, annotations, enums, records, sealed classes and the platform module system.
Questions coming soon
Inversion of control and dependency injection, bean configuration and the application context lifecycle, Spring Boot, REST controllers and the @Component, @Autowired, @Transactional and @RestController annotations.
Questions coming soon
JDBC and connection pooling, JPA and Hibernate, entity mapping, transactions and common query performance pitfalls.
Questions coming soon